That depends on whether or not you set the Axe Fx as your default sound interface or not, I think.I could be mistaken; but system sounds no longer get routed through the Axe. So that's a big plus. As those were always rather, um; loud. Because that's my favorite way to play.
On MacOS, I believe LoopBack from Rogue Amoeba will do what you need. This app allows you to create a virtual output device that you can use to merge and reroute audio, and that has a level control for all audio going from the computer to the AxeFX that is missing if you simply use the AxeFX as your output device.Is there a workaround for adjusting the computer audio volume that is returned to USB 1/2? Computer is very loud compared to the guitar sound. So far, I’ve had to make sure to adjust volume sliders on all apps or videos before pressing play.